“There is a sense of going too far and too much and becoming so ubiquitous that people don't consider you something special,” Rubin told NBC White House correspondent Kristen Welker. “She is the first lady for goodness sakes. She's not just a Hollywood celebrity."

Obama will hit the road this week to promote the third anniversary of her “Let’s Move” campaign to fight childhood obesity. The two videos she released last week with Big Bird, the Sesame Street character who became a political football during the presidential campaign, highlighted her efforts to encourage kids to eat healthy and become more active.

She then literally acted out her “Let’s Move” motto on the late-night circuit when she performed a dance skit with Jimmy Fallon.

New York Times journalist Jodi Kantor, author of the book “The Obamas,” said the appearances are part of a carefully crafted public relations plan.

"It's almost as if her real strategy is a kind of charm offensive that is then intended to build support for her husband's initiatives,” she said.

Like all first ladies, Obama is trying to develop a second-term agenda that won’t distract from her husband’s. But she's probably feeling a confidence in her role that may not have been present in her first term, said Anita McBride, who served as chief of staff to Laura Bush.

“The difference between a first term and a second term really is the fact that you've got your grounding,” she said. “All of the lessons learned of a first term, now you can pick up and have the freedom to really act.”

Obama aides won’t reveal much about her plans for the next few years, other than saying they will share details in the next few months. In addition to her anti-obesity campaign, she’s also expected to continue her work to help military families.

“The one rule that Michelle Obama always follows is that she never wants to distract from her husband's agenda,” Kantor said.

“It’s possible that she might address tougher, more controversial issues, but I do not believe based on what aides have told me that she would do it if she thought that she was going to cause a furor and distract from what her husband was trying to get done.”